西南地区夏季降水和印度洋海温的关系

Relationship between Summer Precipitation Variation in Southwest China and Indian Ocean SST

摘要: 为研究印度洋海温变化对西南地区夏季降水的影响，利用西南地区76个气象站点1961~2022年共62年夏季逐日气象观测降水量资料、同期Hadley全球月平均海表温度资料，网格距1˚ × 1˚，以及同期NCEP-NCAR月平均再分析格点资料，网格距2.5˚ × 2.5˚，通过合成分析、EOF分解、SVD分解、相关分析等方法，详细分析了西南地区夏季降水变化和印度洋海温的关系。结果表明：(1) 西南地区夏季降水量的显著相关区域位于孟加拉海湾，阿拉伯海海温附近的中印度洋海域(30˚~105˚E, 30˚N~40˚S)。(2) 海温偏暖年时，西南地区夏季降水集中于渝，贵地区；海温偏冷年时，西南地区夏季降水主要集中于西南地域中部地区以及成都平原附近；且海温偏暖年的降水量远多于偏冷年。(3) 当印度洋春冬两季海温异常偏暖(冷)的时候，西南川渝贵地区同年夏季降水量异常偏多(少)，而云南地区则相反；当印度洋夏季海温异常偏暖(冷)的时候，川北，川中和渝贵地区同年夏季降水量异常偏多(少)；而云南北部和川南地区相反。(4) 降水偏多年，西南地区位势高度为负异常值，大气稳定性差，低层水汽通量辐合强度大，散度为负且绝对值大，水汽来源充足，且风场和水汽通道方向一致利于降水；偏少年，西南地区位势高度为正，水汽来源少，水汽辐合强度小，大气层结稳定，不易产生强对流天气。

Abstract: To study the impact of sea surface temperature changes in the Indian Ocean on summer precipitation in the southwestern region, 62 years of daily meteorological observation precipitation data from 76 meteorological stations in the southwestern region from 1961 to 2022 were used, as well as global monthly average sea surface temperature data from Hadley during the same period. The grid distance was 1˚ × 1˚, and the monthly average reanalysis grid data of NCEP-NCAR during the same period, with a grid distance of 2.5˚ × 2.5˚. The relationship between summer precipitation changes in the southwestern region and Indian Ocean sea surface temperature was analyzed in detail through methods such as synthesis analysis, EOF decomposition, SVD decomposition, and correlation analysis. The results show that: (1) The significant key area of the correlation between summer precipitation in the southwestern region and Indian Ocean sea surface temperature is the central Indian Ocean region near the Arabian Sea and the Bay of Bengal (30˚E~105˚E, 30˚N~40˚S). (2) When sea surface temperature shows abnormal warming, summer precipitation in the southwest region is concentrated in Chongqing and Guizhou regions; when the sea surface temperature is abnormally cold, the summer precipitation in southwest is mainly concentrated in the middle of southwest China and near Chengdu Plain; and the precipitation in warm years is much higher than that in cold years. (3) When sea surface temperatures in the Indian Ocean are anomalous and warmer or colder during the spring and winter seasons, the Chongqing, Sichuan, and Guizhou regions experience more or less precipitation during the following summer season, while the Yunnan region experiences the opposite. When the Indian Ocean sea surface temperature is warmer (colder) during the summer season, the northern part of Sichuan, the central part of Sichuan, and the Chongqing and Guizhou regions experience more (less) precipitation during the following summer season, while the northern part of Yunnan and the southern part of Sichuan experience the opposite. (4) The precipitation is more than years old, the geopotential height in the southwest region is negative outlier, the atmospheric stability is poor, the low level water vapor flux convergence intensity is large, the divergence is negative and the absolute value is large, the water vapor source is sufficient, and the wind field and the water vapor channel direction are consistent in favor of precipitation; as years with less precipitation, the southwest region has a positive geopotential with few sources of water vapor, low intensity of water vapor convergence, stable atmospheric stratification, and not conducive to generating strong convective weather.